Removing Metal from Rails 3.

If you have existing Metals, you have a few options:
* if your metal behaves like a middleware, add it to the
  middleware stack via config.middleware.use. You can use
  methods on the middleware stack to control exactly where
  it should go
* if it behaves like a Rack endpoint, you can link to it
  in the router. This will result in more optimal routing
  time, and allows you to remove code in your endpoint
  that matches specific URLs in favor of the more powerful
  handling in the router itself.

For the future, you can use ActionController::Metal to get
a very fast controller with the ability to opt-in to specific
controller features without paying the penalty of the full
controller stack.

Since Rails 3 is closer to Rack, the Metal abstraction is
no longer needed.

actionpack/lib/action_dispatch.rb

@@ -43,7 +43,6 @@ module ActionDispatch
 
   autoload_under 'middleware' do
     autoload :Callbacks
-    autoload :Cascade
     autoload :Cookies
     autoload :Flash
     autoload :Head

actionpack/lib/action_dispatch/middleware/cascade.rb

-module ActionDispatch
-  class Cascade
-    def self.new(*apps)
-      apps = apps.flatten
-
-      case apps.length
-      when 0
-        raise ArgumentError, "app is required"
-      when 1
-        apps.first
-      else
-        super(apps)
-      end
-    end
-
-    def initialize(apps)
-      @apps = apps
-    end
-
-    def call(env)
-      result = nil
-      @apps.each do |app|
-        result = app.call(env)
-        break unless result[1]["X-Cascade"] == "pass"
-      end
-      result
-    end
-  end
-end

railties/guides/source/configuring.textile

@@ -63,8 +63,6 @@ h4. Rails General Configuration
 
 * +config.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then used to log information from Action Controller. Set to nil to disable logging.
 
-* +config.metals+ accepts an array used as the metals to load. If this is set to nil, all metals will be loaded in alphabetical order. If this is set to [], no metals will be loaded. Otherwise metals will be loaded in the order specified 
-
 * +config.plugin_loader+ overrides the class that handles loading each plugin. Defaults to +Rails::Plugin::Loader+.
 
 * +config.plugin_locators+ overrides the class that handle finding the desired plugins that you‘d like to load for your application. By default it is the +Rails::Plugin::FileSystemLocator+.

railties/guides/source/initialization.textile

@@ -668,7 +668,6 @@ This file requires _rails/railtie.rb_ which defines +Rails::Railtie+.
 * add_routing_namespaces
 * add_locales
 * add_view_paths
-* add_metals
 * add_generator_templates
 * load_application_initializers
 * load_application_classes
@@ -726,7 +725,6 @@ This file is used to set up the +Rails::Paths+ module which is used to set up he
       paths.app.helpers         "app/helpers",         :eager_load => true
       paths.app.models          "app/models",          :eager_load => true
       paths.app.mailers         "app/mailers",         :eager_load => true
-      paths.app.metals          "app/metal",           :eager_load => true
       paths.app.views           "app/views",           :eager_load => true
       paths.lib                 "lib",                 :load_path => true
       paths.lib.tasks           "lib/tasks",           :glob => "**/*.rake"
@@ -3154,7 +3152,6 @@ This method is defined like this:
       middleware.use('ActionDispatch::Cookies')
       middleware.use(lambda { ActionController::Base.session_store }, lambda { ActionController::Base.session_options })
       middleware.use('ActionDispatch::Flash', :if => lambda { ActionController::Base.session_store })
-      middleware.use(lambda { Rails::Rack::Metal.new(Rails.application.config.paths.app.metals.to_a, Rails.application.config.metals) })
       middleware.use('ActionDispatch::ParamsParser')
       middleware.use('::Rack::MethodOverride')
       middleware.use('::ActionDispatch::Head')
@@ -3288,7 +3285,7 @@ Finally, a +Rails::Application::Configuration+ object will be returned. On this
 <ruby>
   attr_accessor :after_initialize_blocks, :cache_classes, :colorize_logging,
                 :consider_all_requests_local, :dependency_loading,
-                :load_once_paths, :logger, :metals, :plugins,
+                :load_once_paths, :logger, :plugins,
                 :preload_frameworks, :reload_plugins, :serve_static_assets,
                 :time_zone, :whiny_nils
 
@@ -3574,7 +3571,6 @@ The +super+ method it references comes from +Rails::Engine::Configuration+ which
       paths.app.controllers     "app/controllers",     :eager_load => true
       paths.app.helpers         "app/helpers",         :eager_load => true
       paths.app.models          "app/models",          :eager_load => true
-      paths.app.metals          "app/metal"
       paths.app.views           "app/views"
       paths.lib                 "lib",                 :load_path => true
       paths.lib.tasks           "lib/tasks",           :glob => "**/*.rake"

railties/guides/source/rails_on_rack.textile

@@ -222,57 +222,6 @@ use MyOwnStackFromStratch
 run ActionController::Dispatcher.new
 </ruby>
 
-h3. Rails Metal Applications
-
-Rails Metal applications are minimal Rack applications specially designed for integrating with a typical Rails application. As Rails Metal Applications skip all of the Action Controller stack, serving a request has no overhead from the Rails framework itself. This is especially useful for infrequent cases where the performance of the full stack Rails framework is an issue.
-
-Ryan Bates' "Railscast on Rails Metal":http://railscasts.com/episodes/150-rails-metal provides a nice walkthrough generating and using Rails Metal.
-
-h4. Generating a Metal Application
-
-Rails provides a generator called +metal+ for creating a new Metal application:
-
-<shell>
-$ rails generate metal poller
-</shell>
-
-This generates +poller.rb+ in the +app/metal+ directory:
-
-<ruby>
-# Allow the metal piece to run in isolation
-require(File.dirname(__FILE__) + "/../../config/environment") unless defined?(Rails)
-
-class Poller
-  def self.call(env)
-    if env["PATH_INFO"] =~ /^\/poller/
-      [200, {"Content-Type" => "text/html"}, ["Hello, World!"]]
-    else
-      [404, {"Content-Type" => "text/html", "X-Cascade" => "pass"}, ["Not Found"]]
-    end
-  end
-end
-</ruby>
-
-Metal applications within +app/metal+ folders in plugins will also be discovered and added to the list.
-
-Metal applications are an optimization. You should make sure to "understand the related performance implications":http://weblog.rubyonrails.org/2008/12/20/performance-of-rails-metal before using it.
-
-WARNING: To continue the Metal chain execution, return an +X-Cascade+ HTTP header with a value of +pass+.
-
-h4. Execution Order
-
-All Metal Applications are executed in alphabetical order of their filenames, so +aaa.rb+ will come before +bbb.rb+ in the metal chain.
-
-You can override the default ordering in your environment. Simply add a line like the following to +config/application.rb+
-
-It is, however, possible to override the default ordering in your environment. Simply add a line like the following to +config/environment.rb+
-
-<ruby>
-config.metals = ["Bbb", "Aaa"]
-</ruby>
-
-Each string in the array should be the name of your metal class. If you do this then be warned that any metal applications not listed will not be loaded.
-
 h3. Resources
 
 h4. Learning Rack

railties/lib/rails/application.rb

@@ -27,7 +27,7 @@ module Rails
   # Besides providing the same configuration as Rails::Engine and Rails::Railtie,
   # the application object has several specific configurations, for example
   # "allow_concurrency", "cache_classes", "consider_all_requests_local", "filter_parameters",
-  # "logger", "metals", "reload_engines", "reload_plugins" and so forth.
+  # "logger", "reload_engines", "reload_plugins" and so forth.
   #
   # Check Rails::Application::Configuration to see them all.
   #
@@ -36,17 +36,15 @@ module Rails
   # The application object is also responsible for holding the routes and reloading routes
   # whenever the files change in development.
   #
-  # == Middlewares and metals
+  # == Middlewares
   #
-  # The Application is also responsible for building the middleware stack and setting up
-  # both application and engines metals.
+  # The Application is also responsible for building the middleware stack.
   #
   class Application < Engine
     autoload :Bootstrap,      'rails/application/bootstrap'
     autoload :Configurable,   'rails/application/configurable'
     autoload :Configuration,  'rails/application/configuration'
     autoload :Finisher,       'rails/application/finisher'
-    autoload :MetalLoader,    'rails/application/metal_loader'
     autoload :Railties,       'rails/application/railties'
     autoload :RoutesReloader, 'rails/application/routes_reloader'
 
@@ -83,7 +81,7 @@ def method_missing(*args, &block)
       end
     end
 
-    delegate :middleware, :metal_loader, :to => :config
+    delegate :middleware, :to => :config
 
     def require_environment!
       environment = paths.config.environment.to_a.first

railties/lib/rails/application/configuration.rb

@@ -9,7 +9,7 @@ class Configuration < ::Rails::Engine::Configuration
 
       attr_accessor :allow_concurrency, :cache_classes, :cache_store,
                     :encoding, :consider_all_requests_local, :dependency_loading,
-                    :filter_parameters,  :log_level, :logger, :metals,
+                    :filter_parameters,  :log_level, :logger,
                     :plugins, :preload_frameworks, :reload_engines, :reload_plugins,
                     :secret_token, :serve_static_assets, :session_options,
                     :time_zone, :whiny_nils
@@ -45,10 +45,6 @@ def middleware
         @middleware ||= app_middleware.merge_into(default_middleware_stack)
       end
 
-      def metal_loader
-        @metal_loader ||= Rails::Application::MetalLoader.new
-      end
-
       def paths
         @paths ||= begin
           paths = super
@@ -157,7 +153,6 @@ def default_middleware_stack
           middleware.use('::ActionDispatch::ParamsParser')
           middleware.use('::Rack::MethodOverride')
           middleware.use('::ActionDispatch::Head')
-          middleware.use(lambda { metal_loader.build_middleware(metals) }, :if => lambda { metal_loader.metals.any? })
         end
       end
     end

railties/lib/rails/application/metal_loader.rb

-require 'action_dispatch'
-
-module Rails
-  class Application
-    class MetalLoader
-      attr_reader :paths, :metals
-
-      def initialize
-        @paths, @metals = [], []
-      end
-
-      def build_middleware(list=nil)
-        load_metals!(list)
-        self
-      end
-
-      def new(app)
-        ActionDispatch::Cascade.new(@metals, app)
-      end
-
-      def name
-        ActionDispatch::Cascade.name
-      end
-      alias :to_s :name
-
-    protected
-
-      def load_metals!(list)
-        metals = []
-        list = Array(list || :all).map(&:to_sym)
-
-        paths.each do |path|
-          matcher = /\A#{Regexp.escape(path)}\/(.*)\.rb\Z/
-          Dir.glob("#{path}/**/*.rb").sort.each do |metal_path|
-            metal = metal_path.sub(matcher, '\1').to_sym
-            next unless list.include?(metal) || list.include?(:all)
-            require_dependency metal.to_s
-            metals << metal
-          end
-        end
-
-        metals = metals.sort_by do |m|
-          [list.index(m) || list.index(:all), m.to_s]
-        end
-
-        @metals = metals.map { |m| m.to_s.camelize.constantize }
-      end
-    end
-  end
-end

railties/lib/rails/engine.rb

@@ -25,7 +25,7 @@ module Rails
   #   end
   #
   # Then ensure that this file is loaded at the top of your config/application.rb (or in
-  # your Gemfile) and it will automatically load models, controllers, helpers and metals
+  # your Gemfile) and it will automatically load models, controllers and helpers
   # inside app, load routes at "config/routes.rb", load locales at "config/locales/*",
   # load tasks at "lib/tasks/*".
   #
@@ -73,7 +73,6 @@ module Rails
   #     paths.app.controllers     = "app/controllers"
   #     paths.app.helpers         = "app/helpers"
   #     paths.app.models          = "app/models"
-  #     paths.app.metals          = "app/metal"
   #     paths.app.views           = "app/views"
   #     paths.lib                 = "lib"
   #     paths.lib.tasks           = "lib/tasks"
@@ -202,10 +201,6 @@ def eager_load!
       end
     end
 
-    initializer :add_metals do |app|
-      app.metal_loader.paths.unshift(*paths.app.metals.to_a)
-    end
-
     initializer :load_config_initializers do
       paths.config.initializers.to_a.sort.each do |initializer|
         load(initializer)

railties/lib/rails/engine/configuration.rb

@@ -19,7 +19,6 @@ def paths
           paths.app.helpers         "app/helpers",         :eager_load => true
           paths.app.models          "app/models",          :eager_load => true
           paths.app.mailers         "app/mailers",         :eager_load => true
-          paths.app.metals          "app/metal",           :eager_load => true
           paths.app.views           "app/views"
           paths.lib                 "lib",                 :load_path => true
           paths.lib.tasks           "lib/tasks",           :glob => "**/*.rake"

railties/lib/rails/generators/base.rb

@@ -288,7 +288,7 @@ def self.base_name
         end
 
         # Removes the namespaces and get the generator name. For example,
-        # Rails::Generators::MetalGenerator will return "metal" as generator name.
+        # Rails::Generators::ModelGenerator will return "model" as generator name.
         #
         def self.generator_name
           @generator_name ||= begin

railties/lib/rails/generators/rails/metal/USAGE

-Description:
-    Cast some metal!
-
-Examples:
-    `rails generate metal poller`
-
-        This will create:
-            Metal: app/metal/poller.rb

railties/lib/rails/generators/rails/metal/metal_generator.rb

-module Rails
-  module Generators
-    class MetalGenerator < NamedBase
-      check_class_collision
-
-      def create_metal_file
-        template "metal.rb", "app/metal/#{file_name}.rb"
-      end
-    end
-  end
-end

railties/lib/rails/generators/rails/metal/templates/metal.rb

-# Allow the metal piece to run in isolation
-require File.expand_path('../../../config/environment',  __FILE__) unless defined?(Rails)
-
-class <%= class_name %>
-  def self.call(env)
-    if env["PATH_INFO"] =~ /^\/<%= file_name %>/
-      [200, {"Content-Type" => "text/html"}, ["Hello, World!"]]
-    else
-      [404, {"Content-Type" => "text/html", "X-Cascade" => "pass"}, ["Not Found"]]
-    end
-  end
-end

railties/lib/rails/tasks/framework.rake

@@ -37,7 +37,7 @@ namespace :rails do
       project_templates = "#{Rails.root}/lib/templates"
 
       default_templates = { "erb"   => %w{controller mailer scaffold},
-                            "rails" => %w{controller helper metal scaffold_controller stylesheets} }
+                            "rails" => %w{controller helper scaffold_controller stylesheets} }
 
       default_templates.each do |type, names|
         local_template_type_dir = File.join(project_templates, type)

railties/test/application/metal_test.rb

-require 'isolation/abstract_unit'
-
-module ApplicationTests
-  class MetalTest < Test::Unit::TestCase
-    include ActiveSupport::Testing::Isolation
-
-    def setup
-      build_app
-      boot_rails
-
-      require 'rack/test'
-      extend Rack::Test::Methods
-    end
-
-    def app
-      @app ||= begin
-        require "#{app_path}/config/environment"
-        Rails.application
-      end
-    end
-
-    test "single metal endpoint" do
-      app_file 'app/metal/foo_metal.rb', <<-RUBY
-        class FooMetal
-          def self.call(env)
-            [200, { "Content-Type" => "text/html"}, ["FooMetal"]]
-          end
-        end
-      RUBY
-
-      get "/not/slash"
-      assert_equal 200, last_response.status
-      assert_equal "FooMetal", last_response.body
-    end
-
-    test "multiple metal endpoints" do
-      app_file 'app/metal/metal_a.rb', <<-RUBY
-        class MetalA
-          def self.call(env)
-            [404, { "Content-Type" => "text/html", "X-Cascade" => "pass" }, ["Metal A"]]
-          end
-        end
-      RUBY
-
-      app_file 'app/metal/metal_b.rb', <<-RUBY
-        class MetalB
-          def self.call(env)
-            [200, { "Content-Type" => "text/html"}, ["Metal B"]]
-          end
-        end
-      RUBY
-
-      get "/not/slash"
-      assert_equal 200, last_response.status
-      assert_equal "Metal B", last_response.body
-    end
-
-    test "pass through to application" do
-      app_file 'app/metal/foo_metal.rb', <<-RUBY
-        class FooMetal
-          def self.call(env)
-            [404, { "Content-Type" => "text/html", "X-Cascade" => "pass" }, ["Not Found"]]
-          end
-        end
-      RUBY
-
-      controller :foo, <<-RUBY
-        class FooController < ActionController::Base
-          def index
-            render :text => "foo"
-          end
-        end
-      RUBY
-
-      app_file 'config/routes.rb', <<-RUBY
-        AppTemplate::Application.routes.draw do |map|
-          match ':controller(/:action)'
-        end
-      RUBY
-
-      get "/foo"
-      assert_equal 200, last_response.status
-      assert_equal "foo", last_response.body
-    end
-  end
-end

railties/test/application/middleware_test.rb

@@ -82,12 +82,6 @@ def app
       assert_equal "Rack::Config", middleware.first
     end
 
-    test "shows cascade if any metal exists" do
-      app_file "app/metal/foo.rb", "class Foo; end"
-      boot!
-      assert middleware.include?("ActionDispatch::Cascade")
-    end
-
     # x_sendfile_header middleware
     test "config.action_dispatch.x_sendfile_header defaults to ''" do
       make_basic_app

railties/test/application/paths_test.rb

@@ -38,7 +38,6 @@ def assert_not_in_load_path(*path)
 
     test "booting up Rails yields a valid paths object" do
       assert_path @paths.app.models, "app", "models"
-      assert_path @paths.app.metals, "app", "metal"
       assert_path @paths.app.helpers, "app", "helpers"
       assert_path @paths.app.views, "app", "views"
       assert_path @paths.lib, "lib"
@@ -73,7 +72,6 @@ def assert_not_in_load_path(*path)
       assert_in_load_path "vendor"
 
       assert_not_in_load_path "app", "views"
-      assert_not_in_load_path "app", "metal"
       assert_not_in_load_path "config"
       assert_not_in_load_path "config", "locales"
       assert_not_in_load_path "config", "environments"

railties/test/generators/metal_generator_test.rb

-require 'generators/generators_test_helper'
-require 'rails/generators/rails/metal/metal_generator'
-
-class MetalGeneratorTest < Rails::Generators::TestCase
-  include GeneratorsTestHelper
-  arguments %w(foo)
-
-  def test_metal_skeleton_is_created
-    run_generator
-    assert_file "app/metal/foo.rb", /class Foo/
-  end
-
-  def test_check_class_collision
-    content = capture(:stderr){ run_generator ["object"] }
-    assert_match /The name 'Object' is either already used in your application or reserved/, content
-  end
-end

railties/test/railties/shared_tests.rb

@@ -241,24 +241,6 @@ def test_i18n_files_have_lower_priority_than_application_ones
       assert_equal "1", I18n.t(:bar)
     end
 
-    def test_plugin_metals_added_to_middleware_stack
-      @plugin.write 'app/metal/foo_metal.rb', <<-RUBY
-        class FooMetal
-          def self.call(env)
-            [200, { "Content-Type" => "text/html"}, ["FooMetal"]]
-          end
-        end
-      RUBY
-
-      boot_rails
-      require 'rack/test'
-      extend Rack::Test::Methods
-
-      get "/not/slash"
-      assert_equal 200, last_response.status
-      assert_equal "FooMetal", last_response.body
-    end
-
     def test_namespaced_controllers_with_namespaced_routes
       @plugin.write "config/routes.rb", <<-RUBY
         Rails.application.routes.draw do